Means and method for controlling refrigerator temperature



Jan. 28, 1936. c. w. BONDURANT MEANS AND METHOD FOR CONTROLLING REFRIGERATOR TEMPERATURE Filed oet. 4, 1952A 2 Sheets-Sheet 1 PULL To sToP C) PUSH To START 1N VEN TOR.

Car/fon l/Bona'uran.

@7 T 7 ATTORNEY.

C. W. BONDURANT MEANS AND METHOD FOR CONTROLLING REFRIGERATOR TEMPERATURE Jan. 28, 1936.

Filed OCC. 4, 1932 2 Sheets-Sheet 2 L RooM Tl-IrlPERATUREA FOOD COM PARTNENT TEMP,

`INVENTOR. Car/fon WBonc/uran.

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ATTORNEY.

Patented Jan. 28, 1936 PATENT OFFICE MEANS AND METHOD FOR CONTROLLING REFRIGERATOR TEMPERATURE Carlton W. Bondurant, Cleveland, Ohio, assignory to The Bishop & Babcock Manufacturing Company, Cleveland, Ohio, a corporation of Ohio Application October 4, 1932, Serial No. 636,160

15. Claims.

This invention relates to means and methods for controlling the temperature produced by power operated refrigerating apparatus and particularly apparatus of the electric power operated class.

Heretofore in the control of electrically operated refrigerating apparatus, such for example as domestic refrigerators, control devices have been employed responsive to changes of temperature of a refrigerator compartment or of a portion of the refrigerating apparatus, to control the starting and stopping of an electric power supplying motor, to maintain they refrigerator compartment at -substantially a constant temperature, predeterminedlyv adjustable by suitable adjustment means on the control dev'ice.

The power is automatically turned on and oif periodically by the device as the temperature reaches respectively predetermined high and 10W values. The average value is commonly referred to as the temperature range and the temperature difference between the high and low values is commonly referred to as the temperature differential.

In refrigerating apparatus employingrefrigerant circulated through pipes or conduits to absorb heat from the refrigerator' compartment,l

frost usually forms upon the exposed pipes after a period of operation.

c, Heretofore it has been customary in order to remove the frost, to manually effect a so-called defrosting Voperation by shutting down the power and permitting the refrigerator to warm up to a temperature at which kthe frost will melt oi. Such defrosting operation requires attention and -skill to avoid too long continuance thereof and the consequent attainment of a high temperature at which food or the like in the refrigerating compartment will spoil.

It is an object of this invention to provide an improved method and means for controlling refrigerating apparatus whereby defrosting may be effected in an improved manner without danger of attainment of an undesirably high temperature.

Another object is to provide such a method and means whereby, to effect the defrosting operation, the temperature of the refrigerator may be maintained at substantially a predetermined maximum suilicient to eiect defrosting but low enough to preserve food or the like in the refrigerator compartment. r

Another object is to provide, in an automatic power operated refrigerator of the class in which the power is periodically turned oi and on in response to changes of temperature or a control point or station thereof to maintain a predetermined temperature differential and temperature range, improved means to effect a change of temperature range independently of the temperature differential.

Another object is to provide, in an automatic power operated refrigerator ofthe class referred to, improved -means whereby the temperature range may be raised to eiect a defrosting operation while concurrently maintaining the refrigerator at a food preserving temperature and at a predetermined temperature differential.

Another object is to provide an improved thermostatic electric switch device for automatically controlling the electric motor of a motor operated refrigerating apparatus.

Another object is to provide an improved thermostatic electric switch device for automatically controlling the electric'motor of a motor operated refrigeraiing apparatus whereby the above objects may be attained.

Another object is to provide an improved thermostatic electric switch device of the class referred to having improved means to adjustably vary the temperature range independently of the temperature differential.

Another object is to provide an improved electric switch control device for refrigerator motors having improved operable means for stopping the motor for an extended period of time and for starting it up again at the end of that time.

Another object is to provide, in an electric control device for refrigerator motors, improved means for stopping the motor automatically in case of a current overload to the motor.

Another object is to provide, in an electric control device for refrigerator motors, an improved thermally actuatable means for stopping the motor in case of a current overload thereto and improved manually operable means for restarting the motor.

Another object is to provide an improved thermostatic electric switch of the class referred to adaptable to economical manufacture and to eflicient operation.

Another object is to provide such a thermostatic electric switch which is adapted to present an aesthetic appearance when installed in connection with a commercial, domestic or the like Another'object is to provide, in connection with an electric power operated refrigerating apparatus, improved means for adjustably varying the temperature range.

Another object is to provide, in connection with an electric power operated refrigerating apparatus, improved means for adjustably varying the temperature range independently of the temperature differential.

Another object is to provide a methodl and apparatus for effecting defrosting or frost prevention in a refrigerating apparatus comprising \a compressor while concurrently operating the in the art to which my invention appertains.

My invention is furtherdisclosed in the following description taken in connection with the accompanying drawings, in which:

Fig. 1 is an elevational cross-sectional view of the thermostatic switch device embodying my vention;

Fig. 2 is a view similar to Fig. 1 taken from the opposite side of the parts thereof, and with parts shown in cross-section which are shown in elevation in that figure;

Fig. 3 is a view taken approximately-from the plane 3-3 of Fig. V2;

Fig. 4 is a fragmentary view taken from the plane 4--4 of Fig'. 2;

Fig. 5 is a view taken from the bottom of the parts of Fig. 1 and with a cover thereof removed;

Fig. 6 isa top ,plan view of the device of Fig. l;

Fig. 7 is a view taken from the plane 1-1 of Fig. 6;

Fig. 8 is a fragmentary View taken from the.

plane of the upper face of a plate 62 constituting part of the embodiment of Fig. 1;

Fig. 9 is a fragmentary View` illustrating in elevation a cam element shown in cross-section in Fig. 1;

Fig. 10 is a view similar to Fig. '9 taken from the opposite side thereof; v

Fig. 11' is a fragmentary sectional-view taken from the plane II of Fig. 1; Fig. 12 is a fragmentary sectional view taken from the plane I2-I2 ofFig. 1 and'withv parts thereof omitted for simplicity;

Fig. 13 is a fragmentary view of a thermally releasable latch element which I may employ;

Fig. 14 is a chart illustrating diagrammatically variations of temperature which may result in the operation of or by the adjustment of the apparatus illustrated in the gures and to be described hereinafter. y

Referring to the drawings, I have illustrated generally at I a base and at 2 and 3 housing or cover portions associated with and secured thereto for housing apparatus, mounted upon the base. I'he parts I, 2 and 3 may be formed from Bakelite or other suitable moldable and preferably insulating material.

The base I has a downwardly open .cup portion 4 the lower or open end of which is closed by metal plate 5 and secured` to the cup by screws 6-6 threaded intoV suitable thickened portions of the cup wall.

The plate 5 has sealedly secured thereto the lower end of afthermostatica bellows 1 the upper guessesI nd of which is sealedly closed by a cover or end thrust element 8 to substantially the center of which is rigidly' connected an upwardly extending plunger 9 terminating upwardly in a generally conical point I0 and vertically reciprocable with expansive and contractive movements of the bellows 1 and during its reciprocatory motion, being guided in a bore II in the base I and in the bottom of the cup portion 4.

Communicating with the interior of the bellows 1 through a sleeve I2 on the plate 5 is a flexible tube y.I3 terminating in a bulb I4, and the bellows 1, tube I3 and bulb I4 constitute a sealedly closed chamber into which a predeterminedquantity of thermally expansible fluid may be injected; andby this'construction, as will now be understood by those skilled in this art, when .the bulb I4 is subjected to changes of temperature, the iluid will correspondingly expand or contract and cause, through the agency of the bellows 1, a corresponding vertical movement of the plunger 9.

Thevconical point I0 of the plunger 9'is seated in a corresponding recess in the lower end of a socket member I5 riveted or otherwise rigidly connected to alever I6 formed from sheet metal and having rearwardly, or at its left end as viewed in Fig. 1, a pair of depending ears I1-I1 straddling the upwardly extending-legs I8-I8 of a U-shaped bearing element illustrated generally boss 23circular in configuration to center the lower convolution of a compression spring '24 abutting upon the lever at its lower end.

At its extreme forward end; the lever I 5 has a pair of downwardly extending forks 25-25 provided at their lower ends with pockets/ZE--ZG in which pockets are disposed the leg ends I21 of a U-shaped lever 28, the closed end of the U of which has looped thereinone end of a tensionV spring 29.

Upon up and down movements of the forks 25 f the lever I6 corresponding to movements of v the plunger 9, the pockets 26 will raise or lower the leg ends 21 and cause'the lever to fulcrum over a fulcrum or fulcrums 30 formed upon the upstandinglegs 3I of a U-shaped sheet metal element mounted on the base I to cause the closed end 28 of the lever 21 to snap from an upper to a lower position or-vice versa to change the directionofpull of the spring 29 to correspondingly snap-operate a switch arm 32, to be more fully described.

In its downward position, the closed end of the lever 28 may be stopped upon a post or posts 33.

The switch arm 32 referred to is preferably formed from sheet metal and comprises a pair of rearwardly extending arms 34 which at their rearward or left-hand ends as viewed in Fig.-1 straddle the ears `I1 of the lever I6 and are rotatably mounted'i upon the shaft 22. The-forw`ard ends of the arms 34 are closed by an integral portion 35 having an integral downwardly extending tongue 36 and a pair of forwardly extending arms f 31. The lower end of the tongue 36 is hooked to another rivet-formed contact 42.

the forward end of the spring 29 and thus as the rearward end ofthe spring 29 is raised and lowered as above described, with a. snap-action, the forward end of the switch arm 32 together with the arms 31--31 thereof are moved with a snap movement upwardly or downwardly to switchadapted to bridge and connect a, pair of switch contacts 40 and 4| which are-generally of rivet form, the head of the rivet comprising the contact portion and the shank of the rivet being driven into suitable bores of'metallic bushings 42 and 43 respectively which are pressed or integrally molded into the insulating material of the base I as shown in Fig. 3.

' As will now be understood, up and down snap movements of the switch arm 32 will with a snap movement carry the contact bar 39 out of and into engagement with the contacts 40 and 4| to open and close an electric circuit which may control the electric motor of a refrigerator to stop and start the same.

The bushing 42 has screwed thereinto an electric terminal screw 44 to which one line wire of the circuit may be directly connected. The lower end of the bushing 43 has Adriven thereinto A contact 45 is mounted on the end, see Fig. 2 and Fig. 3, of a switch arm 46 mounted to rock on the base I', being provided with'a transverse grooveV 41 engaging a transverse projection 48 on the base. As viewed in Figs. 2 and 4, the switch arm 46 is con-r strained resiliently to move toward the position to engage the contacts 42 and 45 bya spring 49,' preferably of U-shape, the free end 50 of which engages the end of the lever 46 carrying the contact 45and thevother end of which terminates in an offset ear see Fig. 5, secured rlgidly'to the base I as by a screw 52. The spring 49 thus Vmaintains the contacts 42-45 normally engaged.

I'he switch arm 46 and spring 49 are guided in -their movements lto maintain them in correct alignment and position by a pin 253 projected through suitable elongatedperforations in the lever and spring and driven or originally molded rigidly into the base l' The spring 49 also functions as a current conductor to carry current from the contacts 42-45 when engaged. 'I'he other outgoing leadl terminal, corresponding to the terminal 44,' is p'rovided by a screw53 in a terminal plate 54 rigidly se cured on the base I, see Fig. 5, as by a rivet or screw 55; and the circuit from the screw 52 to the plate 54 is completed through a flat metal heating element 56 connected at opposite ends to the screw 52 and to the plate54 by a screw 51.

As will now be understood, the external circuit, for example to the motor of a refrigerator compressor, and connected tothe switch, device above described by the screws 44 and 53, may be broken or made at thecontacts 40 and 4| automatically by the automatic operation of the switch arm 32 in response' to changes of temperature at a control station on the apparatus or in a refrigerator compartment, through the agency ofthe thermostatic bellows 1.

Means will now be described for effecting control of the circuit manually as desired to either make or break the circuit 'optionally at the contacts 40 and 4|V and also for effecting control of the circuit by automatically breaking it at the contacts 42-45 upon the occasion of a current overload to the motor through the agency of the heating element 56 above referred.

To manually open or close the circuit by means of the contacts 40 and 4|, I provide a vertically reciprocable bar 58 the lower endy of which is guided in a suitable recess 59 in the base l and the upper end of which as at 60 is guided generally in a perforation 6| in a base plate 62 of sheet metal disposed generally parallel to the molded r base I and rigidly connected thereto and maintained in spaced relation therewith by plurality such as two posts 63-63; the lower ends of which are secured in any suitable manner in the material of the base I and to the upper ends of which the plate 62 is secured as by screws 64-64.

The bar 58 is provided with a laterally extending lug 65 and a tension spring 66 is hooked at one end in a perforation in the lug and at the' other end in -a suitable perforation in the plate 62. 'I'he spring thus constantly exerts an upward longitudinal thrust on the bar 58 tending side of the plate as particularly shown in Figs.

2 and 4.

The bar` 58`is provided also with a laterally extending lug 68 normally disposed under and spaced from. a projection 69 provided on the switch arm 32.

Upon movement of the bar 58 toward the right as viewed in Fig. 2, the upper end 60 of the bar willmove into a relatively larger portion of the perforation 6| and the shoulder 61 will be free from the lower edge of the plate asy clearly shown in Fig. 4 and the bar 58 will be 4projected upwardly by the spring 66 and the lug 68 will engage the projection 89 and move the switch arm 32 upwardly breaking circuit at the contacts 40 and 4|.

The tension of the spring 66 is preferably provided suiiicient to prevent switch closing snap action of the switch arm 32 under the impulsion of the relatively light spring 29. 4

To thus tilt the upper end of the bar 58, as above described, the following means is provided. An element 10, preferably formed from sheet metal, has an inclined slot 1| therein through which is projected a pin 12 carried by a bar 13 (to be described later). The element 10 has an upwardly extending post |52 upon which is formed a cylindrical molded handle 14 terminating at its upper end in a push button portion |31 anda neck |38. The cylindrical portion of the handle 14 is guided for vertical movement in a perforation |39 in a cover plate to be referred to. The element 10 has also a tongue I 40 projected through a perforation |4| in the bar 58 and a shoulder |42 disposed adjacent the side of the bar 58. 'i

By this construction, when the handle 14 is pulled upwardly manually by means of the head |31 and neck |38, the element 19 by means of the slot 1| lon the pin 12 will have a vertical and concurrent lateral movement toward the right as viewed in Fig. 2, causing the shoulder |42 to push it will re-engage the ratchet wheel; and vif in the uponthe bar 58 and release the shoulder 61 as above described, whereupon the element 10 will be moved upwardly along with the bar 58 by means of the spring 66. Y, This will cause the handle 14 to project farther out of the perforation |39 (see dotted lineposition in Fig. 7) and serves as an indication that this operation, including opening of the contact by theA switch arm 32, has been effected. 1

Upon depressing the handle 14 by pushing manually upon the button |31, the element 10 will move downwardly, the tongue |48 will engage the lower periphery of the perforation |4|, the bar 58 will be moved downwardly until the shoulder 61 is brought below the surface of the plate 62, whereupon the spring 66, acting upon the lug 65,' will rock the upper end of the bar 58 to re-engagev the shoulder 61 with the plate to hold the bar 58 downward in its normal position.

The operation thus described of-opening the contacts 48 and 4| may be effected whenever it .is desired to shut down the refrigerating appa- Vtically reciprocable bar 13, preferably formed from sheet metal, has riveted to its lower end as at |44 a piece of insulating material |45 carrying on its lower end a ratchet pawl |46 and adjacent its lower end a lug |41 which maybe in the form ofl a metal rivet.

The pawl 46 is adapted to hook into and engage one or another of the teeth |48 of a ratchet Wheel |49 normally supported rigidly and nonrotati'vely upon the base lby being rotatably mounted (see Fig. 13) upon a pin |58 rigidly secured to and projecting from a flange |5| of the base but normally being prevented from rotation by being soldered to the pin |58 in 'the ratchet wheel bore.

An end portion of the bar 13 opposite the ratchet end ispguided in a perforation |52 in the base plate 62 and is provided with a laterally extending lug |53, and a tension spring |54 is hooked at one end in a'perforation in the llugand at the other end in a suitable perforation in the plate 62. The spring |54 thus constantly exerts an upward thrust on the pawl |46 tending to move the bar |54 upwardly. The lower end of the bar 13 may be guided by disposing the lower portion |45 in a suitable perforation |55 in the base l.

The end of the switch arm 46 opposite the end carrying the contact 45, extends beyond and above the lug |41 on the bar portion |45. When the bar 13-I45 therefore is projected upwardly by the spring |54 in a manner to be described, the lug |41'engages the switch arm 46, rocks around the fulcrum 48v and removes the contact 45 from thel contact 42 to break the circuit.

Upon the occurrence of an overload of current flowing through the circuit and therefore through the heating element 56, heat is generated in the element and heats the pin |50. The heat is communicated to the solder juncture of the ratchet wheel with the pin and melts the same permitting the ratchet .to rotate. The upward pull of the spring |54 therefore pulls on the pawl 46 and rotates the ratchet thus releasing the bar 13 and causing it to break contact at 42-45 in the manner above described.

Upon cessation of current, the heating element cools, the solder hardens, and upon moving the meantime the overload condition .has been removed, the ratchet wheel will hold the bar 13 downwardly and maintain the circuit closed.

Upon thermal release of the ratchet wheel |49 as above described, the spring |54, projecting the l bar 13 upwardly, causes the pin 12 mounted thereon and engaging the upper end of the slot 1|, to move upwardly `the element 10 andthe handle 14, 'causing the handle as above described to indicate that the device has thus operated.

The upward movement of the element 10 thus occasioned does not operate to release the bar 58, because the movement of the plate is vertical only.

The bar 13 may, asy will be understood, be returned to re-engage the pawl |46 by pushing downwardly manually on the button |31.

The perforation |4| inthe bar 58 may be suciently long to accommodate the straight vertital movement of the vtongue |48 therein when the element 10 is moved upwardly as just described.

From the foregoingdescription it will be understood that the temperature of the bulb I4 or of the uid therein and in the bellows 1 necessary to raise the lever i6 to cause it to move up sufliciently to rock the lever 41 around the fulcrum 30 and snap the left end, as viewed in Fig. 1, of the spring 29 downwardly suiciently to snap the switch arm 32 downwardly to close the lcontacts as above described and vice versa toopen the contacts, will be determined by the pressure on the lever I6 of the spring 24.

Means will now be described to vary the tension of the spring24 for operative results to vary the temperature range above referred to, and means will also be described to establish adjustably a desired differential as above referred to.

A vertically disposed relatively large diameter shaft 15 longitudinally grooved or splined as at 16 upwardly from the lower end over a portion of its length, has a reduced diameter neck portion11 projected upwardly through a relatively closely fitting perforation in the plate 62, thus providing a shoulder at the lower end of the neck portion 11, abutting upon the lower side of the plate 62, preventing upward axial movement of the shaft 15.

An externally threaded sleeve ,19 slidable axially on the shaft 15 is prevented from rotary movement on the shaft by a pin secured thereto and projecting into the spline 16.

inner bore of the bushing 19 may be splined correspondingly with the shaft 15. Upon the threads of the bushing 19 is'a threaded nut element 8| having an annular flange 82 upon which the upper end of the spring 24 abuts.

The flange 82 has, in its periphery, a pair of diametrically opposite recesses -83-83 embracing the posts 63-63 to prevent rotation of the nut eles ment 8|. Y

ABy this construction it will be seen that when the shaft 15 is rotated in a manner to be described, the bushing 19 will rotate with it and the nut element 8| will be propelled axially of the bushing to vary the tension of the spring 24,

To rotate the shaft 15, its reduced neck portion 11 on the upper extreme end thereof is splined as at 84, Figs. 1 and 11, and a handle element 85 `comprising a head 86, a laterally radially extending-handle 81, and indicating finger 88 opposite the handle, has also a depending cup portion 89 provided with axially disposed interior splines 90 adapted to mesh with the splines 84. By this construction, by rst removing the handle element 85, it may be first rotated into any angular bar 13 downwardly in a mannerv to be described, position relative to the shaft 15 and then "tele- If desired, the

cr. v

Aspectively; and the lugs 2,028,893 scoped therewith by the splines 84-90 to rigidly connect it with the shaft 15 in any rotated position relative thereto for adjustment purposes. After engagement by means of the splines, the shaft 15 may be turned by the handle 81.

By means of the spline adjustment above referred to, the handle 81 (see Figs. 6 and 7), may be rotatably positioned, until the handle is disposed in a right angle or normal central position at which-the tension of the spring 24 is such as to respond to an upper and a lower temperature to 'correspondingly open and close the switch contacts to maintain a normal or desired tempera.- ture range. If it be desired to decrease the temperature range, the handle 81 may be turned in the direction indicated by the legend Colder and the accompanying arrow in Fig. 6. This will have the eifect of turning the shaft 15 and releasing tension on the spring 24 by causing the nut element 8| to travel upwardly.

By employing a multiple thread on the bushing 19, I find that a convenient complete range of Colder adjustments may be effected by substantially a half revolution of the thread by the handle 81.

By turning the handle 81 in the reverse direction, that is in the direction of the legend Defrost and the 4accompanying arrow, high temperatures will result which may be employed to effect the so-called defrosting operation.

I have found' in practice that it is desirable to have a wider scale of `adjustment for temperatures above the normal running or colder temperatures. By the traveling nut 8| and its associated parts, where one-half revolution' of the adjusting handle 81 is employed to regulate the cold and running temperature for ordinary purposes, one one-half revolution is left for the higher adjustment purposes. By the construction now to be described, this remaining half revolution is rendered operative to effect temperature changes more sensitively `vthan for the neck whereby the rotative position of the cam may be adjusted relative to the shaft.

` The cam is provided with two'camming surfaces and 96 of general helical configuration and disposed on relatively larger and relatively smaller ideal cylindrical surfaces coaxial with the' shaft 15. A cam follower 98 has a body portion 99 perforated to encircle the shaft 15 below the partition 68 and between the partition and the upper end of the bushing 19 and therefore adapted to abut upon the bushing end.'

Rising upwardly from the body portion 99 is a pair of upstanding lugs |00 and |0|, the upper ends of which engage the said cam surfaces re- |00 and |0| project through the plate 62 through suitable perforations |02 and |03 therein, Figs. 1 and 8, and the engagement of the lugs with the periphery of the perforations prevents rotation of the cam follower relative to the cam.

Upon rotation of the cam, it will now be clear thatthe reaction of the cam on the upper ends of the lugs `|00 and |0| will move downwardly the cam follower 98 and with` it the bushing 19 which will carry downwardly with it the nut element 8| and compress the spring 24. This downward movement of the nut element, being occasioned by the rotation of the shaft 15 to rotate the cam, occurs concurrently with a. downward movement of the same nut element 8| by the rotation of the shaft and rotation of the v bushing 19. That is to say, the bushing 19 has a rotary movement with the shaft 15 and an axial movement thereon giving a multiplied or very rapid downward movement of the nut element and compression of the spring.

Thus, for a counter-clockwise movement of the handle 81, Fig. 6, the spring is compressed more rapidly for a given rotational movement than upon clockwise rotation from the middle position illustrated in which, as will be understood, the cam is not in operation. `To this end, the cam is provided with dwell portionsr |04 and |05 corresponding to those positions in which the handle 81 is moved clockwise from its central position illustrated.

The shaft'15 is preferably bored out axially, the lower end of the bore being relatively small. The upper end of the bore is `threaded and a plug |01 having a screw-driver slot |08 for adjustment is threaded thereinto and engages the upper end of a compression spring |09 disposed in the bore, the lower end of the spring abutting upon acollar |0, on a pin the pin above the collar having a portion extending into the spring tc center it and the portion below the collar projecting out of the bore as at 2.

The length of the pin is such that when the lever I6 moves upwardly, it will engage the pin and carry the collar 15 away from the shoulder I3 and compress the spring |09; and that when the lever moves downwardly, it will at or adjacent the lower end of its movement leave the pin end ||2 and cause the collar 15 to rest upon the shoulder 3. The tension of the spring 09 may be adjusted by adjustment of the position of the plug |01.

By this construction, the upward movement of the lever I6 in the direction to effect closure of the switch will be initiated at a temperature at which the spring 24 alone will respond. As the lever moves upwardly it picks up the tension of the spring |09 and as it continues to move upwardly it finally reaches theI point at which the snap action at the switch occurs and closes theswitch. Thus the ,closure of the switch occurs at a temperature responsive to the pressure of both springs. When the temperature starts down again, it reaches a point at which the two alone. Thus the switch closes at a temperature corresponding to both springs and opens at a temperature corresponding only to the spring 24.

By adjusting the tension of the spring |09, the difference between the opening and closing temperatures, or temperature diiferential, may be adjusted and thereafter changes of tension of the. spring 24 alone to effect an adjustment of range temperature may be made substantially without changing the differential.

The cover 3 in the form illustrated comprises a side wall or walls I5 which rests upon the base and a connecting top wall I6 which may have embedded therein in spaced portions thereof, threaded bushings ||1 whereby the structure as a Whole may be connected to a frame element or elements I|8 by screws H9 projected i through the frame element into the bushings I1.

To hold the wall portions ||5 upon the frame I, threaded studs having enlarged heads |2| may be projected through the top portion H6 and into threaded perforations in the plate 02. The enlarged head portions |2| may also be threaded and screws |22 threaded thereinto, projected through perforations in a cover plate'l23.

The heads of the screws |22 and the cover plate |23 may be ornamented as desired as may also be the head 86 and handle 81. The cover plate may conceal all the otheroperative parts and render the exposed appearance aesthetic and in harmony with other designed parts of the refrigerator., Y v

Preferably, the end of the handle 14 is given a distinctive color such as red and is disposed so l as to project through the perforation |39 of the cover plate |23 at such a point as to be opposite the indicating end or finger 88 of the handle 01 and may provide the indicating point on the scale Ordinates represent temperature and abscissae 1 time. Beginning at the left-hand of the diagram, .the temperature points |30 4and |3| indicate the low andhigh temperatures at which the switch successively responds, the difference between these two temperatures being the aforesaid differential. These temperatures may be the temperature to which' the bulb I4 is exposed. The 1temperature of the,4 refrigerator compartment which does not respond as quickly to starting and stopping of the refrigeration compressor, and which may besubstantially constant, is

illustrated by the substantially constant line of temperature |32. As a line of comparison, the line |33 represents the higher room temperature. 'I'he temperature |32 is therefore the so-called range temperature.

The range temperature |32 may be adjusted y by moving the handle 81 upon the portion of the adjustment scale 'indicated by the legend Colder, By moving the handle equal steps of adjustment, the values |30 Aand |3| maybe changed to |30', 13| or to |30" and I3!" etc., the average range at these new adjusted positions being respectively higher. In the right-hand portion of the diagram Fig. 14 is illustrated the result of moving the lever 81 counter-clockwise and into the Defrost zone of adjustment. As be seen, for' equal steps of adjustment, the average or range changes more rapidly than in the other part of the adjustment zone. Bothv the upper and lower temperatures as at |34 and |35 have been raised but the difference therebetween, or the so-called temperature differential, is substantially the same as at |30|3|. The range is changed to the higher value indicated at |36. The average value between |30- |3| may be raised as high as desired toeffect the defrosting operation; Correspondlngly, 'the refrigerator temperature |38 will be raised as indicated in the chart. i

As will be observed in the chart, substantially equal relatively smallchanges are eifected by adjustment in the Colder part of the scale, as

- for example lgoing from'200 to 20| or from 202 may be operated to maintain in theV refrigeratorv compartment any desired normal refrigerating temperature range within limits for ordinary operation: and that if frost should form or tend to form upon an exposed refrigerant carrying conduit of thel apparatus, it may be melted olf, not by shutting down the compressor in the ordinary manner of the prior art. but by adjusting the operating temperature to a point at which frost will melt or not form while maintaining the on and oi periodic operation of the compressor, under the control of the differential temperature actuated switch device. Adjustment is provided in theA thermostatically operated switch device, whereby whereupon a single revolution of an adjusting handle, an adjustment of temperatures over much greater extent of variation than heretofore possible is provided. Improved means is also provided to shut down and start up again the compressor motor if it should be desired so to control it and improved means to shut down the compressor upon the occurrence of an overload, both such means being operable by a single push-button type of controller handle automatically signaling the circuit condition.

In the temperature chart, Fig. `14, the temperature curves are merely illustrative of the general character of the changes of temperature indicated thereby and are not intended to be accurate as to the actual relative temperatures indicated by the ordinates of the diagram.-

My invention is not limited to the exact details of construction shown and described. Many changes and modifications may be made within the scope and spirit of my invention without sacriiicing its advantages.

I claim:

1. In a thermally actuatable switch construction, a thermostat comprising an element movable -ment, a`threaded element rotatable by the operable element, a second threaded element meshed therewith movable thereby to adjust the spring tension upon rotary movement in onedirection, and a cam lrotatable by the rotatable element hav.- ing a cam follower adapted to adjust the spring tension upon rotary movement in the other direction.

2. A thermostatically actuatable switch construction as described in claim 1, and in which the rate of change of the spring tension for rotary movement in one direction is greater than the rate for movement in other direction.

3. A thermally actuatable switch construction as described in claim 1, and in which the rate of change of adjustment when rotation is in the dil rection to eifect adjustment by the cam is greater than in the other direction.

4. A thermally actuatable switch construction as described in claim l, and in which the adjustment when theioperable element is moved in one direction is by the screw threads alonev and in the other direction is bythe screw threads and the cam concurrently.

5. A thermally actuatable switch construction as -described in claim l, and in which the spring tension is changed by a traveling nut on a rotatable screw rotatable by the operable rotary element when rotated in one direction and by the same traveling nut ,moving by the concurrent action of the rotating screw threads and also by a'cam when the rotatable element is rotated in the other direction.

6. In a switch of the class described, a thermostatically movable switch contact controlling arm, a spring opposing thermostatic movement' of the arm in one direction, means for adjusting the tension of the spring comprising a rotatable shaft, a sleeve axially and non-rotatively movable on the shaft, a traveling nut threaded on the sleeve, adapted when it travels to change the tension of the spring, a handle for turning the shaft to effect traveling of the nut in either direction, a cam rotatable with the shaft, having a dwell surface and a camming surface, a cam follower movable axially of the shaft, and engaging the sleeve and adapted to move the cam follower to move the sleeve axially of the shaft to change the tension of the spring, whereby when the shaft is rotated in one direction through a part of a revolution it may change the tension of the spring by the traveling nut independently of the cam and when rotated in the other direction through another part of the revolution may effect traveling of the nut and variation of spring tension concurrently by the screw threads and-by the cam follower.

'7. In a thermally actuable switch construction, a thermostat, a switch member movable by the thermostat responsive to temperature changes thereof, opposing means opposing thermally effected movement by the thermostat, an element movable to vary the opposition of the opposing means, and adjusting means for adjustably moving the movable element comprising a rotarily and bodily movable element engaged with 1the movable element to move it relative thereto when rotated and to move it therewith when moved Y bodily, and means for rotarily and bodily moving the movable element.,

8. In a thermally actuable switch construction, a thermostat, a switch member movable by the thermostat responsive to temperature changes thereof, opposing means opposing thermally effected movement by the thermostat, an element movable to vary'the opposition of the opposing means, and adjusting means for adjustably moving the movable element comprising a rotatably and axially movable element, engageable with the movable element to move it relative thereto when rotated and to move it therewith when axially moved, and means for rotatably and axially moving the movable element.

9. In a thermally actuable switch construction, a thermostat, a switch member movable by the thermostat responsive to temperature changes thereof, opposing means opposing thermally effected movement by the thermostat, an element movable to vary the opposition of the opposing means, and adjusting means for adjustably moving the movable element comprising a rotary operating element, an intermediate element movable rotarily upon rotary movement of the operating element in one direction and movable bodily upon rotary movement of the operable element in the other direction, and means for transmitting rotary and bodily movement of the intermediate element to the movable element.

10. In a thermally actuable switch construction, a thermostat, a switch member movable by the thermostat responsive to temperature changes thereof, opposing means opposing thermally eifected movement by the thermostat, an element movable to vary the opposition of the opposing means, and adjusting means for adjustably moving the movable element comprising a rotary operating element, an intermediate element movable rotarily upon rotary movement of the operating element in one direction and movable axially upon rotary movement of the operating element in the other direction, and means for transmitting rotary and axial movement of the intermediate element to the movable element.

11. In a thermally actuable switch construction, a thermostat, a switch member movable by the thermostat responsive to temperature changes thereof, opposing means opposing thermally effected movement of the thermostat, an element movable to vary the opposition of the opposing means, and adjusting means for adjustably moving the movable element comprising a rotary operating element, an intermediate element movable rotarily upon rotary movement of the operating element in one direction and movable axially and rotarily upon rotary movement of the operating element in the other direction and means for transmitting rotary and axial movement of the intermediate element to the movable ele- I ment.

12. A thermally actuable switch construction as described in claim 9 and in which the movement of the movable element by the intermediate element is greater for a unit of movement of the operating element in one direction than in the other.

13. In a thermally actuable switch construction, a thermostat, a switch member movable by the thermostat responsive to temperature changes thereof and having a predetermined extent of movement, opposing means opposing thermally effected movement by the thermostat, an element movable to vary the opposition of the oppart only of the switch member movement, and

means for adjusting the opposition of the second opposing means independently of the adjustment of the first-named opposing means.-

14. In a thermally vactuable switch construction, a thermostat, a switch member reciprocatorily movable by the thermostat responsive to temperature changes thereof, opposing means opposing thermally effected movement of the thermostat, an element movable to vvary the 'opposition of the opposing means, and adjusting means for adjustably moving the movable element-comprising a rotary operating element, an

intermediate element movable rotarily upon rotary movement of the operating element in` one direction and movable bodily upon rotary movementof the operable element in the other direction, and means for transmitting rotary and bod- A ily movement of the intermediate element to the movable element, and a second opposing means.

eiected movement by the thermostat, an element movable to vary the opposition of the opposing means, and adjusting means for adjustably moving theu movable element comprising a rotary operating element, an intermediate element movable rotariILv upon rotary movement of the operating element in one direction and movable bodily upon rotary movement of the operating element in the other direction; means for transmitting rotary and bodily movement of the intermediate element to the movable element, and the rotary operating element eiecting greater movement of the movable element for a unit of movement of the operating element in one direction than for a. unit of movement thereof in the other direction, and a second opposing means eiective during a part only of the switch member movement and means for adjusting the opposition of the second opposing means independently of the adjusting means of the first-named opposing means.

CARLTON W. BONDURANT. 

